34 Gardiner and I to. — On Mucilage-cells 
mucilaginous secretion is entirely intra-protoplasmic, and that 
the cell-wall takes no part whatever in the phenomenon. 
The earliest stage of development of the secretory hairs is 
indicated by the arising of a papillose outgrowth from one 
of the ordinary epidermal cells. This may be a cell occupy- 
ing any position in the case of a young leaf, but in the paleae 
it must be one which is situated along the edge of that 
structure. The papilliform protrusion is soon cut off by a 
transverse wall and may then again divide once or several 
times (Fig. 14). It is always the apical or head-cell which 
exhibits the secretory function. All the cells both of the leaves 
and paleae possess large and distinct nuclei, and numerous 
plastids are also present. No movement of the protoplasm 
of the stalk-cells could be detected as in the case of Ononis 
spinosa , L. 1 Even more markedly than the rest, the young 
gland-cell exhibits the well-defined nucleus and plastids of 
which we have spoken, and here the commencing vacuolation 
and the delicate strands of protoplasm, stretching on all sides 
from the nucleus to the peripheral lining of the cell-wall, 
appear to exquisite advantage and beauty (Fig. 15). As the 
cell grows the usual single vacuole is formed and the proto- 
plasm takes up its well-known position, lining the rapidly 
enlarging cell-membrane as a delicate primordial utricle. 
Both the nucleus and the plastids are then found to be 
situated on the inner side of the ectoplasm as in Char a 2 . 
The secretory change first begins in the endoplasm, com- 
mencing just beneath its free surface and simultaneously over 
the entire area which immediately bounds the cell-vacuole 
(Fig. 16). It then spreads into deeper and deeper layers until 
the whole of the endoplasm takes part in the process. After 
some time the plastids are gravely affected by the various 
changes which are taking place, and they eventually become 
disorganised, and disappear, yielding up their own substance 
to contribute to that of the secretion. In the nucleus also, 
great degeneration occurs, and at the period of rupture of the 
1 Behrens in Ber. deutsch. bot. Gesellschaft, Bd. iv. (1886), p. 402. 
2 Sachs’s Textbook of Botany, 2nd Engl, ed., p. 304. 
